Product Description High speed steel with black oxide coating for corrosion resistance. 5 flute design reduces vibration for smoother drilling. Precision-ground 82 deg (Degree) tip for countersinking into most Machin able metals. 1/4" Round shank compatible with all hand Held and stationary drills. From the Manufacturer High Speed Steel Countersinks, 5/8-inch diameter, milled and precision ground to countersink into any machinable material including iron, steel, soft metals, plastics or wood. Irwin tools are made of only the finest materials, manufactured to exacting tolerances.